The biology, ecology and behaviour of the Bivalve Mysella bidentata (Montagu)

TLDR: Dense Amphiura populations enlarge the water-sediment interface and thereby the oxydized layers and the microbial activity, which benefits Mysella which obtains protection from surface-hunting predators and additional supply of food.

Abstract: Mysella bidentata is a euryvalent species. Its distribution in the N. Oresund 3-4 months after settling is positively correlated with the density of adult Amphiura filiformis. In the laboratory, Mysella prefers to live in the oxydized layers around the burrow of Amphiura. Dense Amphiura populations enlarge the water-sediment interface and thereby the oxydized layers and the microbial activity. This benefits Mysella which obtains protection from surface-hunting predators and additional supply of food. In their second year the bivalves are functional males, and when three years old and 3 mm long they are hermaphrodites. Males produce fertile and oligopyrene sperm simultaneously. Sperm transfer involves sperm bags and receptacula seminis, and is thus time-independent of egg-spawning. Mysella reacts to gravitation by positive or negative taxes, and to direction of water flow by positive tropo-taxis or compass reactions. Chemical stimuli from a predator (Astropecten) evoke direct orthokinesis. Stimuli...